MAXQ7670EVKIT+ Maxim Integrated Products, MAXQ7670EVKIT+ Datasheet - Page 20

• Manufacturer Part Number: MAXQ7670EVKIT+
• Description: KIT EVAL FOR MAXQ7670
• Manufacturer: Maxim Integrated Products
• Series: MAXQ®r
• Type: MCUr

Specifications of MAXQ7670EVKIT+

• Contents: Board
• For Use With/related Products: MAXQ7670
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Microcontroller with 10-Bit ADC,
PGA, 64KB Flash, and CAN Interface
Figure 5. Conversion Timing Differences Between Gain = 1V/V and Gain = 16V/V
The input-capacitance charging rate determines the
time required for the T/H to acquire an input signal. The
required acquisition time lengthens with the increase of
the input signals source resistance. Any source below
5kΩ does not significantly affect the ADC’s perfor-
mance. A high-impedance source can be accommo-
dated by placing a 1µF capacitor between the input
channel and AGND. The combination of analog-input
source impedance and the capacitance at the analog
input creates an RC filter that limits the analog-input
bandwidth.
Use the following methods to control the ADC conver-
sion timing:
1) Software register bit control
2) Continuous conversion
3) Internal timer (T0)
4) External input through ADCCNV
Refer to the MAXQ7670 User’s Guide for more detailed
information on the ADC and mux.
The MAXQ7670 operates from a single, external +5V
supply connected to the DVDDIO. DVDDIO is the sup-
ply rail for the digital I/O and the supply input for both
integrated linear regulators. The +3.3V linear regulator
powers AVDD, while the +2.5V linear regulator powers
DVDD. Alternatively, connect REGEN2 to DVDDIO and
apply external power supplies to AVDD and DVDD.
Power supplies DVDDIO, DVDD, and AVDD each
include a brownout monitor that alerts the µC through
an interrupt when the corresponding supply voltages
drop below a defined threshold. This condition is gen-
erally referred to as brownout interrupt (BOI). Enable
BOI by setting the VABE, VDBE, and VIBE bits in the
20
PGA = 16V/V
SAR CYCLE
PGA = 1V/V
SAR CYCLE
______________________________________________________________________________________
Controlling ADC Conversions
PGA TRACK
7.5 SCLK
POR and Brownout
SAR TRACK
Input Impedance
PGA HOLD, SAR TRACK
6 SCLK
HOLD AND SAR CONVERT
APE register. By continually checking for low supply
voltages, appropriate action can be taken for brownout
conditions.
Once the +5V DVDDIO supply reaches approximately
1.25V, the +2.5V linear regulator turns on and DVDD
begins ramping. Between the DVDD levels of 1V and
the reset threshold, the DVDD monitor holds RESET
low. DVDD releases RESET after reaching the reset
threshold. The MAXQ7670 jumps to the reset vector
location (8000h in the utility ROM). During this time,
DVDD finishes ramping to its nominal voltage of +2.5V.
During this POR time, the software-enabled +3.3V lin-
ear regulator remains off. Turn on the +3.3V linear regu-
lator after the MAXQ7670 has completed its bootup
routines and is running application code. To turn on the
+3.3V regulator, set the LRAPD bit in the APE register
to 0. The AVDD supply begins ramping to its nominal
voltage of +3.3V.
The MAXQ7670 features brownout monitors for the +5V
DVDDIO, +3.3V AVDD, and +2.5V DVDD power sup-
plies. When enabled, these monitors generate interrupts
when DVDDIO, AVDD, or DVDD fall below their respec-
tive brownout thresholds. Monitoring the supply rails
alerts the µC to brownout conditions so appropriate
action can be taken. Under normal conditions the DVDDIO
brownout monitor signals a falling +5V supply before
the DVDD or AVDD brownout monitors indicate that the
+2.5V or +3.3V are falling. The exceptions to this condi-
tion are:
• If either DVDD or AVDD are externally powered and
• If there is some type of device failure that pulls the reg-
the source of power is removed
ulator outputs low without affecting the +5V DVDDIO
supply
HOLD AND SAR CONVERT
Startup Using Internal Regulators
13 SCLK
Brownout Detectors